Experimental results of underground coal gasification of Turkish lignite in an ex-situ reactor

In this study the characteristics of Turkish lignite for underground coal gasification process was experimentally investigated in a laboratory scale ex situ reactor. A rectangular prism shaped ex-situ reactor having 0.65×1.01×2.07m external dimensions was built and used in the experiments, placing lignite blocks and their surrounding strata in it. Coal gasification tests were performed for the Malkara Pirinççesme (Turkey) lignite using air, pure oxygen and steam. The Malkara Pirinççesme lignite is characterized by its high ash, low moisture and high volatile contents. During the gasification experiments, temperature distributions inside the coal seams and syngas flow rates in the outlet were measured. Syngas compositions were analysed using MRU Varioplus Syngas analyser and Agilent 7890B gas chromatograph. Experiments were divided into four stages; (i) the oxygen gasification stage, (ii) the oxygen-air gasification stage, (iii) the oxygen-steam stage, and (iv) the oxygen-air-steam stage. Syngas produced during the oxygen gasification stage was characterized by its high calorific values of 6–9MJ/Nm3, carbon monoxide contents of 23–33 (vol)%, and hydrogen contents of 20–30(vol)%. The results show that syngas produced during the oxygen gasification stage of our experiments has much higher carbon monoxide and lower hydrogen contents than those in the literature.